Compensatory electrical control circuit



COMPENSAT ORY ELECTRICAL CONTROL CIRCUIT Filed Nov. 5, 1947 T0 Oil/1?SECTIONS FRoM Sauna:

I FEEDER- ifi COHPE VSATOKY CONT/70L 5U5- TOLOAD INVENTOR.

Haw/4K0 mew) Patented Aug. 9, 1949 coMrENsAroRY ELEo'rnIoA ooN'rnoCIRCUIT Howard Farley, East Orange, N. J

Application November 5, 1947, Serial No. 784,136

2 la ms- This invention relates toelectrlcal control circuits and more;particularly tocircuits to be employed where automatic potentialregulators are used upon a plurality of feeder circuits which arearranged to ultimately feed acommon load.

Circuit arrangements of this general type are often encountered, innetworkpower distribution systems. Due to fluctuations, ofathe; loaddistribution, or sometimesv to accidental interruption of some one ormore feeder; circuits, the current flow through'various, portions ofthesystem is altered in value: thus cau ing; a corresponding change ofpotential values; at various points of the-network. V

The employment of; automatic potential regu lators located at a,Pluralityof; points, usually where branch feeders-depart fromthemainfeeder lines, is familiar in theart. However; difficulties have arisenfromthispractice,,especlally under conditions, where two or more; suchfeeder circuits, each provided with. an individual and independentpotentiahreglliator, are interconnected via a common load, circuit,which; latter capable of receiving energy simultaneously from all ofsuch feeder circuits-., These difficulties owe their origin to, the factthatv the interconnection just referred. to unavoidably sets up acircuit of the type known. as a loop circuit, through, which latterthere may flowcirculatory currents havingrelatively great magnitudes.owing to the. fact that the interconnection conductors comprising theloop circuit arealmost, invariably of; relatively low impedance, wherebyan unbalance of even relatively small, magnitude in the potentialsappearing at differentpoi-nts; of the loop circuit will cause the flowof circulatory currents having such high values as to represent the lossof a very con side'rable amount oiiene t y, as w ll as. tending t negatethe desired resultto, be obtained by the system, nam'el'y, auniformpotential at various points thereof, since. the IR drops ofpotential caused by the circulatory. currents act. in oppfosition to thedesired regulatory action.

The particular fault-Just described is further complicated by the mannerin which the auto.- matic potential compensators react to the circu-vlatory currents. These. last devices are well known in the art andinclude, as an integral part of their actuating mechanisms, relay typedevices which are sensitive to the quantity of current flowing throughthe feeders. Such regulators are designed, not tokeep the potentialconstant at the exactipoint where they are situated, but rather at somepoint nearer the ultimate load, usually termed the centre ofdistribution, in order that the average potential, of the entire networkmay be kept as constant, as practicable. In order to accomplish thisparticular result, the compensators are deliberately arranged, to affordarising characteristic to the regulatory action, in such fashion that anincrease of, load current will boost the potential at the. feeders, inorder tocompensate for the increased line potential losses between thefeeder and the load, due to increased current flow therebetween. Itisthis particular element of the regulatory mechanism which is the worstsufferer from the presence of these circulatory currents, which mayconveniently be termed parasitic currents, since the. mere presence ofsuch parasitic current causes the regulator to boost the potential,there being ordinarily incorporated in the regulator no elements whichare able to discriminate between the true load current and the parasiticcurrent. Therefore the boosting of potential; will in turn againincrease the parasitic current flow, and this last will react to causefurther boost or potential, until extreme ly abnormal potential values,predicated upon purely fictitious load values are ultimately reached.There likewise flows from this sequence of reactions, the additionaldisadvantage that the various portions of the network no longer dividethe load uniformly, but certain sections, in which the potential hasbeen raised above the average by the hyper-compensatory action justdescribed, will carry more than their share of load, and there may evenresult the triggering of one or more safety devices, such as circuitbreakers or fuses, which last will make matters still worse by throwingthe entire load upon the still connected portions of the feeding system.These latter may then repeat the self-propagating cycle of erroneouscontrol, thereby leading to the cutting off of still other feeders andto still greate": overloading until eventually the entire system mayfail.

Various remedies to prevent the occurrence of the above describedundesired sesuence have been proposed. In one such proposed device, theportion of the regulator which responds to current flow has been endowedwith discriminatory characteristics, so that it will respond only to thetrue load current, and not to the fictitious circulatory currents.However, this solution has not been satisfactory for many reasons. Inthis system, it is immediately found necessary to provide additionalinterconnecting circuits to comprise a so-called circulatingcompensatory network. Not only does this add greatly to the complexityof the system, and the cost thereof, but in turn this newinterconnecting circuit becomes subject to malfunctioning, due tosecondary causes, concerning which it is unnecessary here to amplify.

An amplification of the system just mentioned employs still moreregulatory apparatus in order to minimize these last second magnitudedefects, by which time the complexity and cost of the regulatory systemhave been excessively increased, and the possible sources of functionalfaults have been multiplied to an entirely disproportionate degree.

The present invention secures uniform potential control of network ofthe character specified, while at the same time keeping parasiticcurrent flow at a minimum, without the need of the elaboratecross-regulatory circuits and apparatus demanded by the proposed systemsjust described. By the use of this invention it has been found possibleto reduce the multiplicity of transformers, switches, and other elementsof the hitherto proposed systems to a single metallic conductor, withthe optional use of a single simple switch to remove the. regulatorydevice from the circuit, as is often highly desirable when manualswitching of the network is to be performed, or when some portionthereof is subject to failure.

One object of this. invention is to provide a regulatory circuit of thetype described, which shall be extremely simple, inexpensive and subjectto substantially no operative troubles, since a single stationaryconductor, carrying only a fractional percentage of the true loadcurrent, performs the entire regulatory'action.

, Another object of this inveition is to provide a new and improvedregulatory system for interconnected power circuits having amultiplicity of potential regulators, in which "runaway cumulativeover-regulation is completely avoided, and energy loss due to parasiticcurrent flow is reduced to a negligible amount.

Still another purpose of thi invention is to provide a simpleinterconnection system for use with potential regulated networks,wherein an ancillary bus bar type of connection afiords completeequalization of potential control throughout the network, and entirelyavoids the difficulties and dangers of over-regulation, or falseregulation, at any point of the network.

Other purposes and advantages of this invention will be apparent tothose skilled in the art from the. following description, and from thedrawing annexed thereto.

The drawing is of a schematic nature and for simplicity and a clearershowing of the invention proper, certain elements which are well knownin the regulator art are indicated diagrammatically, ince the physicalconstruction thereof bears no essential relationship to the operation ofthi invention. 7 f V The drawing shows a single phase main feeder line,supplyinga common load via three interconnecting feeder lines. It is tobe understood that this is merely an isolated section of a typicalnetwork, wherein many more interconnecting lines may be used, without inany way changing the operation of this invention. Likewise it is to beunderstood that in the case of a polyphase distribution system, all theelement of this invention are to be duplicated upon each phase of thesystem.

By actual operation of the system of this invention over an-extendedperiod of time under various conditions, upon typical power networks, ithas been found that it may be adapted for use upon any potential,frequency or number of phase commonly employed for power distribution.However for best operative characteristics, it has been found desirablethat the total impedance of the feeder line, from the automaticregulator to the point where it is tied into the load line. should notbe materially less than 5%. As far as known, this is the only limitationof the field of use of the'present invention. v

Reference is now made to the left hand one of the three distributingcircuits shown in the drawing as transferring power from a main feederline I to a single line 2, from which the load is tapped off, asindicated at 3. It is to be understood that the particular number ofbranch circuits shown is purely by way of example, and that a lesser ora greater number may be used without altering the functioning of thesystem.

A transformer 4, of the variable tap secondary type, is bridged acrossfeeders I. One side of this transformer is shown as grounded, but it isto be understood that such grounding, while customary, is not essentialto the operation of the invention. A motor 5, of the reversing type, ismechanically coupled, as indicated by dotted line 6, to the tap changerof transformer 4. The two windings i and 8 are to indicate in aschematic manner the two directions of'motor rotation, it beingunderstood that the motor is stationary when neither winding is excited,and moves the tap changer to the left, for example, when winding 8 isexcited, and to the right whenwinding 1 is excited. Motors of this typeare commonly employed in potential regulators, and detailed descriptionthereof is accordingly thought superfluous. Energy for the operation ofthe motor i derived from transformer 9, bridged across secondary leadsIt of transformer 4. The secondary of transformer 9 has one terminalconnected to a control switch II, which allows the automatic-controlaction'to be suspended when desired, as for the reason previouslymentioned. The other secondary terminal is connected to the commonjunction point of windings I and 8.- From switch I I the circuitproceeds to movable relay armature I3, which a1ter-' natively makescontact with stationary contact is or I4, thereby determining which oneof windings I or 8 shall be excited, and consequently determining thedirection of rotation of motor 5. The means to operate armature I 3 isdiagrammatically indicated by a winding I6. It will be seen that whenwinding I6 is excited with energy sufficient to hold armature I3 in theposition shown, against the retractile action of spring II, regulatorymo-.

tor 5 will remain quiescent. If the current through winding I6 bedecreased, the armature. will be pulled to the left by the spring, andcause the motor to rotate in one direction, while if the winding currentbe increased the armature will travel to the right, thereby determiningrotation of the motor in the opposite direction.

Power for operation of the relay assembly constituted by elements I3,I4, I5, I6 and I1, is derived from a plurality ofsources, in order tosecure the desired combination of determinant factors to bring about thedesired regulation. The determinant representing purely the potential ofthe secondary of transformer 4 is derived from a potential transformerI8, of which the primary winding I 9 is shunted directly across leads I0. The primary and the secondary windings of transformer I8 areinterconnected at one end of each winding, the grounded side, if aground is used, and the unconnected end of the secondary 20 is connectedto winding I6. of the relay. The

retumcircuitfrointhe' other endof "secondary to the other endofwindingt6 is made via a correnttransformer 21', of "which one terminal isc'onnc'ctedto the common point of interconnection 'ofthe-primaryandsecondary windings of transformer l8. From the other'end ofourrenttransformer '2!- the 'circuit passes through the portion of asubstantially non-inductive winding 22, defined by the position-uponthis last winding of a slider-'23. From the point of contact of-slider23aparallel-current path through the lower portion of resistance 22 andthe lowerportion of an inductive winding 24, up to'thepoint of-contactof another'slider 2 5, upon this last winding, and then backtothepoint'ofcommon interconnection of transformers l8 "and 21, isprovided. *By this means'the lowrportions of both the resistive and theinductive windings are placed in series with one another, between thetwo secondary terminals of'transformer 2!. The potential which isavailable to operate the motor relay winding [6 is then determined notmerelyby the potential of transformer l8, but by a potential which is acombination of this last mentioned potential and the potential availablefrom" transformer? I, as modified by the combination inductive andnoninductive shunt existing thereacross. In opera tion, the positions ofsliders 23 and 25 are adjusted in accordance with the characteristics ofthe load connected to leads [0, as Well known in the art, until the neteffect of current flow through the leg of leads ID constituting theprimary of transformer 2| and the secondary winding characteristics, asmodified by the shunt established, yield the desired potential boostingeffect at a chosen distant point, as previously described.

Up to this point, all the elements described are well known in the artand are connected in a conventional fashion. As so connected they aresubject to the difficulties already described, whereby currentscirculate in parasitic fashion from one such potential control unit toanother unit in the system, and thereby give false alterations of thenet potential supplied to winding It, so that the potential of a feederis raised above the correct value, usually in a cumulative fashion.

The elements of this invention proper are now described. From slider 23a connection is made, preferably via a simple switch 26, to acompensatory control bus 21. Reference is now additionally made to theother branch feeder circuits of the drawing. Each of these units issubstantially identical with the one just described, and similarreference numerals are employed to identify similar elements thereof. Ineach branch feeder circuit, the sliders 23, 23' and 23" areinterconnected via the bus 21, the individual switches being used onlywhen it is desired to shift load, add or remove a feeder circuit, or thelike, or when for any other reason it is desired to suspend thecompensatory action of this invention in an individual branch.

In the operation of this invention each potential regulator will respondexactly as before the addition of the compensatory bus, insofar as thepotential derived from transformers I8, I8 and H! are concerned. Howeverit is no longer possible for any one current transformer, as for exampletransformer 2|, to supply to the motor relay a current componentdiffering from that supplied by any other similar current transformer inthe system. This also brings about the result that instead of heavyparasitic currents circulating through the main feeders of the systemand causing upsetting false responses of the individual regulators, byfictitious determinative potentials being induced in the secondarywindingsof the various current transformers used to actuate theregulators, all the potentials thus derived will'be equalized by currentflow along the compensatory bus bar 2?. It might seem thatthislastcurrent flow would itself be a parasitic circulatory current,but upon analysis it can be seen that it differs from the parasiticcurrent flow previously described in at least two important respects.In-the first place, the value of this current flow is so very low, itusually being only a small fraction of one per cent of the currentflowing in the main power leads, that little power is wasted thereby,especially since the potentials found in the regulatory circuits arecomparatively low, while the main feeders, and branch circuits may be ofseveral thousand volts. Furthermore, this circulatory current is keptcompletely away from the main feeders, so that it can in no wiseinterfere with power passing through these latter.

Finally there is to be noted the extremely important distinction betweenthe circulatory currents of 'this'system and those of prior art systems,that While circulatory current flow of the prior art exerted a viciouseffect upon the desired regulatory action, in addition to beingextremely wasteful of power, the cross-currents of the system of thisinvention perform the highly useful function of contributing to thedesired regulatory action. For these reasons it is hardly possibletruthfully to label the compensatory currents of this invention asparasitic, since they perform an extremely useful function and since theenergy dissipated by such currents is of such a low order of magnitudethat it does not ordinarily exceed such values as are consideredreasonable and allowable for purposes of system potential control.

It has been found in practice that the degree of intercontrol affordedby the circuits of this invention is so nearly ideal that it is usuallypossible to switch into the system additional feeder circuits, providedwith potential regulators, without the need of making extremely closemanual adjustments of the potentials thereof, or of the positions of thesliders upon the compensating winding-s, as the compensatory buscurrents of this invention will very quickly equalize conditionsthroughout the entire system, without permitting excessive current flow,which might actuate safety ancillaries connected thereto, such ascircuit breakers or the like.

While there have been shown and described certain embodiments of theinstant invention, it is to be understood that such are by way ofexample and not of limitation. Many modifications and extensions of thecircuits here shown will be apparent to those skilled in the art, andthe scope of this patent is accordingly limited only by the hereuntoannexed claims.

Having fully described and set forth this invention, what is claimed andis desired to be secured by Letters Patent of the United States is:

1. An electrical network including a common load, a plurality of feederssupplying said load, a plurality of variable ratio transformers, onesupplying each of said feeder-s, a potential and a current transformerfor each feeder, and. responsive to both the potential developed by andthe current flowing out of said transformer, a potential-regulatoryrelay actuated by the seriesconnected output of said potential andcurrent transformers, said two transformers having directly andconductively series-connected secondaries; via a substantially resistivepath to said potential-regulatory relay, and additional means forcausing all said ratio varying means responsive to the current flowingout of said transformer to be actuated in accordance with the averagecurrent flowing in all said feeders, said last means comprising a singlecompensatory control bus conductively and directly connected to theterminal of each current transformer which feeds a respective relay viasaid resistive path, whereby current flow through said control buscauses actuation of all the relays according to the average current flowin all the plurality of feeder circuits.

2. An electrical distribution system including a plurality ofalternating current power circuits, separate potential regulators, onein each circuit, for automatically maintaining the potential of all saidcircuits substantially uniform, said circuits being all connected to acommon load so that inequality in the respective potentials causes acirculating current to flow in the system, a separate line dropcompensator located in each circuit and connected to the correspondingpotential regulator thereof, and means for energizing each line dropcompensator by a current representing the average current in all saidplurality of circuits, said means including in each circuit a potentialand a current transformer and a potential-regulatory relay, said twotransformers having directly and conductively seriesconnectedsecondaries, via a substantially resistive path to saidpotential-regulatory relay, and a single compensatory control bus conductively and directly connected to the terminal of each currenttransformer which feeds a respective relay via said resistive path,whereby current flow through said control bus causes actuation of allthe relays according to the average current flow in all the plurality offeeder circuits.

HOWARD FARLEY.

REFERENCES CITED UNITED STATES PATENTS Name Date Minnecl June 22, 1943Number

